1. Field of the Invention
The present invention relates to a semiconductor device used in an inverter.
2. Discussion of Background
An inverter is widely used in various electrical apparatuses for consuming public and industries. For example, in electric automobiles, propelled by a.c. motors, and hybrid cars, propelled by engines and a.c. motors, as illustrated in FIG. 15(c), an inverter 1 is interposed between a motor and a d.c. power source. The inverter 1 is formed by a semiconductor device 2, and a capacitor 10, located outside the semiconductor device 2, as illustrated in a plan view of FIG. 15(a) and a cross-sectional view of FIG. 15(b). The capacitor 10 is necessary to suppress a voltage regulation of ripple of the d.c. power source. The semiconductor device 2 converts a d.c. current to an a.c. current or convert an a.c. current to a d.c. current by switching elements 20 and diodes 21, both of which are mounted on an insulated board 25. In a case of using a three-phase alternating motor, the semiconductor device 2 should have three-phases of U-phase 40, V-phase 41, and W-phase 42. The insulated board 25 is mounted on a heat dissipating plate 60, and the heat dissipating plate 60 is fixed to a casing 50, made of a synthetic resin. A plurality of conductors are inserted and formed in the casing 50 for internal wiring. The conductors are exposed from a front surface of the casing 50 to form P-terminal 30 and N-terminal 31 on a d.c. current side and U-terminal 32, V-terminal 33, and W-terminal 34 on an a.c. current side, wherein the terminals are connected to the switching elements 20 and the diodes 21 by a wiring pattern and aluminum wires (not shown), formed on a front surface of the insulated board 25. A circuit illustrated in FIG. 15(c) is thus fabricated. The d.c. power source is connected to P-terminal 30 and N-terminal 31, and the three-phase alternating motor is connected to U-terminal 32, V-terminal 33, and W-terminal 34 on the a.c. current side.
As described, when the inverter is formed in the conventional semiconductor device, the capacitors 10 are arranged outside the semiconductor device 2, and as illustrated in FIGS. 15(a) and (b), in order to connect electrode terminals 11a and 11b of the capacitor 10 with P-terminal 30 and N-terminal 31 of the semiconductor device, busbars 16 and 17, insulated by an insulating plate 15, become necessary, whereby the number of components forming the inverter is increased, an assemble is onerous, and a cost is increased.
Further, since the capacitor 10 is arranged outside the semiconductor device 2, a wiring path between the capacitor 10 and the switching element 20 inside the semiconductor device 2 is long, an inductance is increased, and it is necessary to increase an electric strength of the elements to withstand a large surge voltage, whereby the cost is increased. Further, in order to suppress a ripple voltage of the d.c. power source caused by the increment of the inductance, it is necessary to increase a capacitance of the capacitor 10, whereby the size of the capacitor 10 and accordingly the size of the inverter 1 become large.
Further, an electrolytic capacitor shaped like a cylinder is generally used to keep a capacitance large, wherein it becomes difficult to effectively use a space, and miniaturization of the inverter 1 is obstructed.
In Japanese Unexamined Patent Publication JP-A-10-285907, an IGBT module is described, wherein an IGBT, a back-flow diode, and a snubber diode are commonly mounted on a planner electrode to reduce a path of wiring from a smoothing capacitor to a module, the planner electrode is mounted on a metallic plate through an insulating plate, and the metallic plate, a snubber capacitor, a gate circuit, and a protection circuit are commonly accommodated in an outer casing.
However, since the capacitors are arranged outside the conventional inverter, the number of components of the inverter is increased, an assemble is onerous, and a cost is increased.
Further, in the IGBT module, disclosed in JP-A-10-285907, it is necessary to locate the smoothing capacitors outside the IGBT module to form an inverter, and there is a limit in reducing an inductance of wiring from the smoothing capacitors to the IGBT module. Therefore, it is necessary to provide the snubber capacitors to suppress a surge voltage, whereby the number of components of the inverter is increased, an assemble is onerous, the size of the IGBT module is increased, the size of the smoothing capacitor is increased, and accordingly the size of the inverter is increased as a whole.
It is an object of the present invention to solve the above-mentioned problems inherent in the conventional technique and to provide a semiconductor device having a built-in smoothing capacitors in order to miniaturize the capacitors by reducing wiring inductances and resultantly miniaturize a power conversion device (inverter) as a whole.
Another object of the present invention is to reduce the number of components and make an assemble easy.
According to a first aspect of the present invention, there is provided a semiconductor device comprising P-electrodes and N-electrodes; and
capacitors in a form of flat plate or block, connected to a plurality of phases, respectively connected to switching elements and diodes,
wherein a single or a plurality of the capacitors are respectively connected to the P-electrodes and the N-electrodes.
According to a second aspect of the present invention, there is provided the semiconductor device according to the first aspect of the invention,
wherein each of the P-electrodes and each of the N-electrodes are electrically connected between the switching elements and the capacitors through interphase connecting conductors.
According to a third aspect of the present invention, there is provided the semiconductor device according to the second aspect of the invention,
wherein the number of the interphase connecting conductors is at least two,
one of the interphase connecting conductors is connected to each of the P-electrodes,
the other interphase connecting conductor is connected to each of the N-electrodes, and
the interphase connecting conductors are closely arranged so as to be mutually overlapped.
According to a fourth aspect of the present invention, there is provided the semiconductor device according to the third aspect of the invention,
wherein the interphase connecting conductors are shaped like a flat plate.
According to a fifth aspect of the present invention, there is provided the semiconductor device according to the fourth aspect of the invention,
wherein an insulating plate is provided between the interphase connecting conductors, shaped like a flat plate.
According to a sixth aspect of the present invention, there is provided the semiconductor device according to the fifth aspect of the invention,
wherein the interphase connecting conductors, shaped like the flat plate, are bonded to the insulating plate by a bonding layer.
According to a seventh aspect of the present invention, there is provided the semiconductor device according to the fifth aspect of the invention,
wherein the interphase connecting conductors are formed in a printed wiring board.
According to an eighth aspect of the present invention, there is provided the semiconductor device according to the sixth or seventh aspect of the invention,
outer electrodes on one side of the capacitors are connected to one of the interphase connecting conductors, and
the other outer electrodes of the capacitors are connected to the other interphase connecting conductors.
According to a ninth aspect of the present invention, there is provided the semiconductor device according to the second aspect of the invention,
wherein slits are formed in a casing of the semiconductor device, and
the interphase connecting conductors are aligned and supported by the slits.
According to a tenth aspect of the present invention, there is provided the semiconductor device according to the first aspect of the invention,
wherein the capacitors are supported by a supporting plate.
According to an eleventh aspect of the present invention, there is provided the semiconductor device according to the first aspect of the invention,
wherein a plurality of capacitors are fixed to a side surface or both surfaces of the supporting plate.
According to a twelfth aspect of the present invention, there is provided the semiconductor device according to the tenth or eleventh aspect of the invention,
wherein slits are formed in the casing of the semiconductor device, and
the supporting plate is registered and supported by the slits.
According to a thirteenth aspect of the present invention, there is provided the semiconductor device according to the tenth or eleventh aspect of the semiconductor device,
wherein the supporting plate is made of an insulating material, a plurality of conductors, electrically insulated, are monolithically formed in the supporting plate, and
the capacitors are connected to the P-electrode and N-electrode through the conductors.
According to a fourteenth aspect of the present invention, there is provided the semiconductor device according to the tenth or eleventh aspect of the invention,
wherein the conductors are formed so as to be mutually overlapped on both surfaces of the supporting plate, made of the insulating material,
ones of outer electrodes of the capacitors are connected to the P-electrode through the conductors, formed on one of surfaces of the supporting plate; and
the other outer electrodes of the capacitors are connected to the N-electrode through the conductors, formed on the other surface of the supporting plate.
According to a fifteenth aspect of the present invention, there is provided the semiconductor device according to the tenth or eleventh aspect of the invention,
wherein an impedance of a current path between various portions of the outer electrodes of the capacitors and P-electrode or N-electrode of a power module is substantially uniformalized.